Method and arrangement for signaling over alternating current networks



A. YTTERBERG March 7, '1939.

METHOD AND ARRANGEMENT FOR SIGNALING OVER ALTERNATING CURRENT NETWORKS sSheets-Sheet 1 INVENTUR I Filed Deb. 10, 1934.

V- E N v m H T h T r E A March 7, 1939. A. YTTERBERG ,149,

METHOD AND ARRANGEMENT FOR SIGNALING OVER ALTERNATING cunREN'r nm'wonxsFiled Dec. 10) 1954 3 Sheets-Sheet 2 'l-NV ENTER ATTORNEY Patented Mar.7, 1939 ICE PATENT METHOD AND ARRANGEMENT FOR- SIGNAL- ING OVERALTERNATING CURRENT NET- WORKS Arle Ytterberg, Vasteras, Sweden,assignor to Allmanna Svenska Elektriska Aktiebolaget,

Vasteras, Sweden, a corporation of Sweden Application December 10, 1934,Serial No. 756,809 In Sweden December 11, 1933 3 Claims.

The present invention relates to a method and devices for signaling,remote control or the like over power networks by means of a modulatedalternating voltage superimposed on the constant voltage of the networkand with the same frequency as the network voltage.

The invention is mainly characterized in that the signals sent out onthe network are received by a coaction between the constant voltage andthe modulated superimposed voltage in apparatus comprising a fieldsubstantially excited by the constant voltage and. a coil substantiallytraversed by a current caused by the said modulated superimposedvoltage.

The invention is further characterized by a special device forgenerating the superimposed signaling voltage, a device consisting of analternating current generator connected to the network and provided witha field winding, which is fed from one or a plurality of exciters, whichhave a D. C. wound armature, and a field winding connected in serieswith a condenser or an apparatus acting as a condenser.

According to one form of the invention, the apparatus serving to receivethe signals are provided with contact devices mechanically tuned to themodulating frequencies of the superimposed signaling voltage.

The invention will be readily understood by reference to theaccompanying drawings where- Fig. 1 shows a set of machines for agenerator imposing a modulated signaling voltage on the network.

Fig. 2 shows a modified set of machines for generating such a signalingvoltage.

Fig. 3 is a vector diagram showing the different voltages of the machineset of Fig. 1.

Fig. 4 is a wave diagram showing thesignaling voltage in relation to theconstant voltage of the network.

Fig. 5 is a diagram showing the constant voltage and signaling voltagein the case where the modulating frequency is higher than the frequencyof the normal voltage.

Fig. 6 shows a receiving relay used in the points of the network, wherethe signal voltage is comparatively high.

Fig. 7 shows a receiving points of the network where the signal voltagevariations have been damped and replaced by corresponding changes in thecurrent.

Fig. 8 is a vector diagram showing the differ- 55, ent voltages actingin the receiving relay of Fig. 6.

relay used in those Figs. 9 and 10 are wave diagrams explaining theaction of the relay of Fig. 6.

InFig. 1, l is the network and Z is a synchronous machine or astationary transformer, connected to the network I giving a voltageopposing the line voltage. In the case where 2 is a rotating synchronousmachine, 2 designates the field winding of this machine, which is fed inknown manner from a direct current source. This current is then of sucha magnitude, that the voltage generated in the synchronous machine isequal to and opposing the voltage of the network. In the neutral pointof the machine or transformer, which is opened, another transformer 3 isinserted. The winding 4 of this transformer 3 is connected to theneutral point and may be shunted by a switch 5, when no signals are tobe sent out. The other winding 6 of the transformer 3 is connected tothe armature winding 1 on an alternating current machine 8, which isstarted by a direct current electric motor 9. The excitation winding ll]of the machine 8 is connected in series with a direct current generatorH, which latter has for its purpose to compensate the armature reactionin the machine 8, and is in series with two special alternating currentgenerators l2 and I3,-to accomplish the necessary modulation. In thecase of a signal voltage modulated with only a single frequency one ofthese machines of course may be omitted, and the diagrams, Figs. 3, 4and 5, on the drawings refer to the case where the signal voltage ismodulated with only a single frequency. The machines l2 and I3 consistof armatures with commutators and direct current windings movable in thefields of laminated magnets which are excited by the excitation windingsIt and I5 respectively. These field windings are connected in serieswith condensers I6 and II respectively. When the machines are out offunction the switches 18 and I9 are open and the condensers l6 and I!are maintained charged over the resistances 20 and 2| from the samedirect current source which feeds the motor 9. The charging circuits forthe condensers l6 and I! are the following: the terminal on the fieldwinding of generator 9, resistances 20 or 2!, condensers it or H, fieldwindings M or l5, armatures of machines l2 or I3, common terminal forswitches l3 and I9, back to the terminal of the field winding ofgenerator 9. These switches l8, l9 are also used for determining thebeginning and end of the signal impulses, but other means may also beprovided for this purpose.

When the switches l8 and H! are closed the windings l4 and I5 and thearmatures of the machines l2 and I3 are traversed by currents from thecondensers l6 and I7, and these currents continue as alternatingcurrents with frequencies determined by the capacity of the condensersand the reactance of the field windings. These currents cause voltagesin the armatures of the machines l2 and I3 respectively with the samefrequencies as the frequencies of the currents in the windings l t andI5. These alternating voltages cause an alternating current through thefield winding In of the machine 8 and the alternating voltage generatedin the winding '1 by these currents is transmitted to the winding of themachine 2 over the transformer 3. The direct current generator ll servesonly the purpose of giving a constant direct current compensating thearmature reaction from the winding 1.

In the arrangement shown in Fig. 2, 22 designates a machine for thegeneration of the signal voltage which is displaced 90 in relation tothe network voltage. This machine consists of a stator with analternating current winding 23 and a rotor 24 with 4 sliprings and adirect current winding. This machine is excited partly with a constantdirect current from a directcurrent generator 25 which gives a fieldwhich in the stator winding gives rise to a voltage opposite to the linevoltage and equal thereto. The machine is also partly excited with amodulated alternating current from the generators 26 and 21 which are ofthe same type as those described in connection with Fig. 1. The voltagefrom the enerators 26 and 2'! is led to the rotor 24 in twodiametrically disposed points perpendicular to the two diametricallydisposed points to which the generator 25 is connected. The current fromthese machines therefore gives rise toa field displaced 90 in space withrespect to the field generated by the current from the generator 25.Hence the field excited by generators 25 and 2'! induces a voltage inthe stator winding 23, which is displaced 90 with respect to the line ornet-.

work voltage. The machine 22 is started to synchronous speed by a motor28.

In Fig. 3 the vector 30 represents the normal voltage of one of thephases of the network, and 3| is the current vector corresponding tothis voltage. 32 is the voltage corresponding to the armature reactionin the machine 8, and 33 is a voltage induced in the machine 8 by thecurrent from the generator ll. Over the latter voltage the modulatedvoltage induced by the current from the generators l2 and I3 issuperimposed, said voltage being represented on the diagram by thevector 34. The resulting voltage on the network is represented by thevector 35. The vector 36 represents the active power which 'is takenfrom the net l. By'a variation of the size of this vector by a loadingof the machine 8 by means of the machine!) the vectors 33 and3fl may beturned until they become perpendicular to the vector 30. In most casessuch a turning is not necessary.

As seen in the diagram Fig.3 a variation of the size of the vector 34signifies a change of the phase angle between the vectors 3B and 35. Ifthe change in size of the vector 34 is periodic and if the vector 30 hasa constant angular speed the change of the size of the vector 34 isequivalent to a periodical variation of the angular speed of the vector35. The vector 34 begins at the end of the vector 36 and alters betweenthe limits designated by 34 and 34". The real meaning of this variationof the angular speed is illustrated by Fig. 4, which shows the variationof the signal voltage if it is modulated only in accordance with asimple 'sine curve. The curve 3'! shows the alternating voltage on thenetwork in the case that the vector 34 is zero. The curve 38 shows theresulting voltage, corresponding to the vector 35, in the case that thesize of the vector 34 is altered in accordance with a low frequency. Asmay be seen from the diagram the voltage 33 is sometimes leading,sometimes laggingthe voltage 3l. The curve 38 thus varies between thelimits given by the curves designated by 37' and 31". The curve 3811shows the superimposed signal voltage separated from the voltage of thenetwork.

The diagrams Fig. 5 show the sine curves corresponding to the conditionswhen the modulation frequency is higher than the frequency of thevoltage of the network and in these diagrams the voltage of the networkwhen no signals are sent out is represented by the curve 31. The curve38 represents the resulting voltage when signals are sent out. 39represents the field of an electromagnet fed from the net, and '40represents the modulated signal voltage. The curve M shows the forceacting on a coil movable in the field 39 and traversed by a currentcaused by the voltage ill. Such a coil is for instance the relay coil 45in the receiving relay shown in Fig. 6, and the curve 42a shows thechange of the. amplitude of the modulated signal voltage 40.

The curve 42b shows the change of amplitude of the force curve 4!.

The curve 42a varies between a positive and a negative value, and thephysical meaning of this is that the voltage ll! changes its phase inthe points A and B. The amplitude of the forcecurve A l varies also butbetween zero and a maximum value and the phase of this curve is alwaysthe same.

In Fig. 6 a receiving relay for the impulses is shown. This relayconsists of an electromagnet 53 with coil 54. The coil 44 is connectedin parallel with a condenser of such a capacity that resonance in thiscircuit is reached for'the frequency of the network voltage. The coil asand condenser 69 are connected to the net in series with a moving coilt5. This coil is rigidly attached to a rod or rib 46 which is suspendedby a leaf spring M attached to its upper end. On the upper end of therod 55 a beam 56 is fastened, and on this beam resonance weights 58 and89 are attached by means of springs 50 and 5|. The

weights are provided with contacts 54, 55 and 51, 58, and between thesecontacts leaf springs 52 and 53 project, said springs being providedwith contacts which cooperate with contacts on the weights 48, 49.

In Fig. 8, which is a diagram illustrating the function of therelay, thevector 6! represents the voltage on the relay. This voltage causes acurrent through the coils inthe relay. 62 represents the current'throughthe coil 44 which with respect to the phaseis nearly perpendicular tothe voltage GI, and 64 represents the current.

through the condenser 60. The current 52 causes a field 63 in the magnet43, and in this field the.

the current 62 and an increase of the current 64. A decrease of thefrequency, on the contrary, causes an opposite alteration of thecurrents 62 and 64. This alteration of the size of the currents causesan alteration of the size and also of the phase position of theresulting current 65 through the coil 45. It is easily shown that onlythe component of the current 65, which is in phase with the field 45,causes a force on the coil 45, which varies with the modulationfrequency of the signal voltage. The component of the current 65, whichis in phase with the voltage 6|, only causes a force on the coil 45,which varies with a frequency equal to the double frequency of thenetwork voltage, the mean value of said force being zero.

In Fig. 9, 6| designates the voltage on the relay. The curve 63 is thefield in the magnet 43 and 65 is the resultant current through the coil45. The force acting on the coil 45 is equal to the product of thecurrent 65 and field 63 and is shown by the curve 66 in Fig. 10. As seenfrom this figure a force is obtained, which varies from a positivemaximum value to a negative. If the frequency of this variation of theforce is the same as the resonance frequency of one of the resonanceweights for example 48 is brought in oscillation so that the spring 52is caused to touch contacts 54 and 55. The intermittent closing of thecontacts may then be used in known manner for closing the circuit ofauxiliary relays, which in turn may be used for different purposes.

In Fig. '7 another connection of the relay is shown. The condenser andthe coil 44 are also, in this case, connected in parallel and connectedto the network, but the coil 45 is connected to the network by means ofa. current transformer 61. In parallel with the coil 45 there isconnected a series resonance circuit, which has for its purpose toprevent or at least to decrease as much as possible the current throughthe coil 45, which resonance circuit is tuned to the same frequency asthe voltage of the network. The current, however, which has the samefrequency as the signal voltage, cannot to any considerable extenttraverse this circuit but must traverse the coil 45. The function is inother respects the same as the function of the relay shown in Fig. 6.

Instead of providing the relay with special members in mechanicalresonance at the modulation frequencies it may be advisable in caseswhen only one modulation frequency is used to tune the movable coilitself in mechanical resonance at the modulation frequency.

I claim as my invention:-

1. A system for electrical signaling or controlling over an electricalalternating current network, which comprises means for superimposingupon the voltage of the network an alternating voltage of the samefrequency as the network voltage, means for modulating the superimposedvoltage, and means for receiving the signals by a coaction between thenetwork voltage and the modulated superimposed voltage in apparatuscomprising a field excited by the network voltage and a coilsubstantially traversed by a current caused by the modulatedsuperimposed voltage.

2. A system for electrical signaling or controlling over an electricalalternating current network, which comprises means for superimposingupon the voltage of the network an alternating voltage of the samefrequency as the network voltage, means for modulating the superimposedVoltage, means whereby the signals are received by a coaction betweenthe constant voltage and the modulated superimposed voltage in apparatuscomprising a field excited by the constant voltage and a coilsubstantially traversed by a current caused by the modulatedsuperimposed voltage, and contact devices mechanically tuned to themodulating frequency or frequencies of the superimposed voltage attachedto the coil traversed by the modulated circuit.

3. A system for electrical signaling or controlling over an electricalalternating current network, which comprises means for superimposingupon the voltage of the network a modulated alternating voltage of thesame frequency as the network voltage, a generator for the saidsuperimposed voltage connected to the network, at least one exciter forexciting the field of the said generator and consisting of generatorswith direct current wound armatures and with field windings connected inseries with condensers, and means whereby the signals are received by acoaction between the constant voltage and the modulated superimposedvoltage in apparatus comprising a field excited by the network voltageand a coil substantially traversed by a current caused by the modulatedsuperimposed voltage.

ARLE YTTERBERG.

